Question

.i)
Taw UI Muun.
A boy of mass 40 kg walks up a flight stairs to a vertical distance
of 12m, in a time interval of 40 s. At what rate is the boy doing
work against force of Gravity?
1. Iringa fara15 NHAM​

Answer 1

$\displaystyle\large\boxed {\sf {P=117.6\ W}}$

The work done by the boy against the force of gravity is provided by his potential energy, i.e.,

$\displaystyle\longrightarrow\sf {W=mgh}$

$\displaystyle\longrightarrow\sf {W=40\times 9.8\times 12}$

$\displaystyle\longrightarrow\sf {W=4704\ J}$

Then the rate of work done by the boy, i.e., his power, is,

$\displaystyle\longrightarrow\sf {P=\dfrac {W}{t}}$

$\displaystyle\longrightarrow\sf {P=\dfrac {4704}{40}}$

$\displaystyle\longrightarrow\sf {\underline {\underline {P=117.6\ W}}}$